As the other lawyers have noted, this procedure is called a motion for severance. That the defendant wants his own trial is not reason enough to grant the motion.

Whether a defendant is entitled to severance depends upon the specifics of his case. Mr. Shapiro is right that these motions rarely succeed, but that's partly because many of them are brought in cases where they are not justified. You haven't told us enough about this case to say whether severance is appropriate here.